A circuit-breaker is a switching device capable of switching on, loading and switching off current under normal circuit conditions, and capable of switching on, loading and switching off current within a specified time under abnormal circuit conditions.
Arc is a gas discharge phenomenon, and is a transient spark produced by current via certain insulating media, such as air. An arc not only has a great destructive effect on contacts, but also prolongs the time of switching off a circuit.
At present, various circuit-breakers have been applied widely in real life. In conventional techniques, circuit-breakers can switch off and insulate quickly under abnormal circuit conditions, the circuit-breakers generally use the air as a medium for insulation, contact separation must reach a long distance to achieve enough degree of insulation, moreover, an arc which is produced during contact separation may easily continue to burn in the air between contacts, and as a result, the contacts are damaged. In general, the circuit-breakers of the conventional techniques have the defects of poor insulation, low arc breaking speed, poor isolation and sealing, and poor arc distinguishing effect.